FIELD OF THE INVENTION
This invention relates to a fluorescence detecting system in which a photosensitive material, which has an affinity to tumors and emits fluorescence when excited by light, is first administered to an organism, they excitation light is projected onto the part to be observed of the organism, and then the intensity of the fluorescence emitted from the photosensitive material and pigment inherent to the organism is measured, or in which the intensity of auto fluorescence emitted from pigment without administering any photosensitive material is measured. The presence of a tumor is diagnosed on the basis of the intensity of the fluorescence measured.